Hydrothermal Disintegration and Extraction of Different Microalgae Species

Michael Nelles,Michael Kröger,Marco Klemm

doi:10.3390/en11020450

Michael Nelles, Michael Kröger

Open Access

https://doi.org/10.3390/en11020450

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Abstract

For the disintegration and extraction of microalgae to produce lipids and biofuels, a novel processing technology was investigated. The utilization of a hydrothermal treatment was tested on four different microalgae species (Scenedesmus rubescens, Chlorella vulgaris, Nannochloropsis oculata and Arthorspira platensis (Spirulina)) to determine whether it has an advantage in comparison to other disintegration methods for lipid extraction. It was shown, that hydrothermal treatment is a reasonable opportunity to utilize microalgae without drying and increase the lipid yield of an algae extraction process. For three of the four microalgae species, the extraction yield with a prior hydrothermal treatment elevated the lipid yield up to six times in comparison to direct extraction. Only Scenedesmus rubescens showed a different behaviour. Reason can be found in the different cell wall of the species. The investigation of the differences in cell wall composition of the used species indicate that the existence of algaenan as a cell wall compound plays a major role in stability.

Highlights

For the production of algal biofuels several obstacles have to be overcome
The species used in this study; Scenedesmus rubescens (S. rubescens), Chlorella vulgaris (C. vulgaris), Nannochloropsis oculata (N. oculata) and Arthrospira platensis
For algae the disintegration process may have an important influence on the fraction of lipids that can be extracted [46]

Summary

Introduction

For the production of algal biofuels several obstacles have to be overcome. A major problem that has to be considered for algae biorefinery and biofuel processes is the break-up of cell walls.The majority of algae species has a very robust cell wall in order to withstand any environmental stress.it is mandatory to have a pre-treatment, which breaks down the cell walls and disintegrates the membrane structure. For the production of algal biofuels several obstacles have to be overcome. A major problem that has to be considered for algae biorefinery and biofuel processes is the break-up of cell walls. The majority of algae species has a very robust cell wall in order to withstand any environmental stress. It is mandatory to have a pre-treatment, which breaks down the cell walls and disintegrates the membrane structure. Several different disintegration processes are known [1,2] but most of them have not been applied yet to algae in an industrial sized environment. Among a variety of processes hydrothermal treatment is a promising possibility. As a great difference to many biomass processing technologies considered today in research and development hydrothermal treatment uses water as reaction medium. Besides the hydrothermal liquefaction and gasification (temperatures of 300 ◦ C and above) of algae [3,4,5,6,7], there have been publications on the utilization of mild hydrothermal conditions (180 ◦ C–250 ◦ C)

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